Advertising drives a large part of our economy—businesses need to make potential customers aware of their offerings and the benefits of those offerings in order to survive. With targeted advertising, businesses can select which consumers will see their advertisements, such as by selecting keywords for their advertisements that will be match to query terms provided by consumers to a public search engine. Targeted advertising is generally better for businesses than general advertising because businesses can pay only to reach the particular consumers who are most likely to be receptive to their overtures. Such targeted advertising is common on the internet, and may be provided adjacent to search results (where the topics of the selected advertisements are matched to keywords in a search query), with content on web sites (where the advertisements displayed on the sites are matched to topics of items displayed by the sites), and in other areas.
Businesses are especially interested in so-called “conversion”—the process of turning an advertising impression into an actual sale or similar transaction. Conversion can be tracked on the internet, for example, by tracking user traffic from viewing an advertisement through a executing a transaction. A relative proxy for conversions may also be had by tracking the number of times that users react affirmatively to an advertisement, such as by clicking on advertisement copy that is shown to a user with search results or elsewhere. Consumers may also respond to an advertisement by physically going to a business or by calling the business on the telephone.